GRiSP 2 – Erlang and Elixir on bare metal | Hacker News Reader

GRiSP 2 – Erlang and Elixir on bare metal

kickstarter.com

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This is neat, I would have loved to see this a few years ago when I was working on a touchpad dimmer that I used Erlang on (the hardware was originally designed to run Linux so it was easy to put Erlang on there but having a lower-cost solution by not requiring Linux would've been great).

Erlang's remote RPC, high-quality CRDT libraries, and hot-code loading made it an incredible technology for implementing IoT software product features.

Would something like this[1] worked for your project?

[1] https://medium.com/@Bettio/atomvm-how-to-run-elixir-code-on-...

Possibly.

This is great! I haven't tried the boards (yet) but it's difficult to find good industrial ready boards out there. Combine that with the difficulty of handling precise & consistent timing below 1 ms in Linux then these boards are a real gem!

Question about Erlang: is it possible to send large blobs of binary data (e.g. video frames) from one process to another with the guarantee that the data is not serialized and the transfer is close to instantaneous?

Binary blobs over 64B are shared with other processes via reference counted pointers, instead of by copy. Of course this only applies to processes inside the same machine.

You can check the official docs: http://erlang.org/doc/efficiency_guide/binaryhandling.html

Not sure if the overall performance but some people have done streaming mpeg on Nerves using the Picam [1].

1: https://github.com/electricshaman/picam/blob/master/README.m...

If your binary is over some threshold (video frames almost certainly qualify) and the processes live on the same node, then the binaries should stay on binheap / refcounted memory and not get copied.

Ok, that's good to know. How would that work for a large tree with many small nodes? Is structural sharing possible between the two processes?

Not a priori. In practice, I'd guess that if we destructure a typical video frame, it will have a header which is somewhat tree-like and a payload which we are not going to touch and decode. In that case, we avoid the copy for the heavy parts of the frame, i.e., the payload.

A good trick is that if you have a full frame from the network, keep a pointer to the full frame. Then decode the header as needed on top. This way, since the frame is full, you are guaranteed that no copy will occur for the frame while you are processing it. Also, the redundancy of the header is likely to be small in overhead with this approach.

About 10 years ago, I did some work in Erlang where I was moving around 16 kilobyte blocks of data. I managed 800mbit at that time on that generation of hardware. The hardware on the board notwithstanding, I think Erlang is much better at handling this nowadays.

As for the structural shaing between nodes: it is possible but only for data which is written very rarely and read quite often. In practice, the copying overhead in typical usage scenarios tend to be much cheaper than what people fear. One reason is that after the copy, you obtain cache locality, though also potential increased cache pressure.

https://news.ycombinator.com/item?id=16842055

How easy is it to do real-time programming in Erlang? Would it be possible to get to 10 microsecond precision, to e.g. reliably drive a stepper motor directly from code?

10us is not generally achievable. Expect the lowest granularity you can get to be in the millisecond range. Erlang provides soft real-time, and under load you might see a process come later to the scheduler. You are guaranteed that the delay is somewhat fair over all processes though.

If you want harder real-time, it is usually better to have a specialized kernel handling that, locked to a CPU core, and then have the Erlang system orchestrate work as a control backplane for that kernel.

That’s one of the exciting points of this board using a true rtos. You can write real time tasks/threads for the RTEMS system. They mention the possibility of future Erlang bindings to do it as well.

I'm mildly interested in industrial-ready boards myself, but my industrial-ready means sitting outside in a hot and high-vibration environment doing signal processing. Everything I've heard about Erlang says it would be great at the networking part, but has no- or lousy- libraries for most number crunching applications.

You can make even an RPi survive harsher conditions with proper housing. Though it’s easier to work with the RPi compute module for that.

What kind of signal processing? The computational libraries are somewhat rough. Though the Elixir communities are slowly adding more libraries, like Matrex (https://github.com/versilov/matrex). It’s surprisingly easy to write C and Rust extensions.

You can include other C libraries (and whatever else you can manage to interface towards via Erlang's C driver interface) using NIFs (native implemented functions) and Erlang port drivers. This means it's entirely possible to use Erlang for the networking and coordination part and special code for the signal processing.

national instruments makes the SoM, single-board RIO, and myRIO products. each has an fpga that can be programmed with labview and/or xilinx tools and a cpu running real-time linux that can be programmed with labview or any other toolchain you want to install on the linux portion. comes ready to interact with hardware of course.

I'm not sure this counts as "bare metal" since it runs in a VM. Though doing it this way is probably cheaper then using an FPGA.

I'm not 100% sure but I think it's not running on a VM in the virtualization sense; by VM they probably mean BEAM, which is a VM in the same sense that JVM or python are VMs.

I was hoping they'd actually made a bare-metal BEAM implementation like the Lisp and Forth hardware that people have made in the past. This device looks like it's Erlang-on-BEAM-on-RTEMS, which is undoubtedly a more practical and useful thing, but less intriguing.

Its not really „on RTEMS“, its more side by side. RTEMS is not a layer between the BEAM and te hardware its just helping by providing threads, TCP stack and file access. From a Erlang NIF or port driver (thats what we use to access the outside world in Erlang and Elxir) you have direct access to hardware registers and e.g. CPU interrupts.

If RTEMS is controlling the execution of your code, your running on or in RTEMS.

Direct hardware access isn't really "bare metal" in the same manner as software running in DOS is not bare-metal. direct-hardware access is provided in both.

RTEMS isn't "controlling" the execution of the code, it just supplies implementation for OS-specific utilities (effectively the POSIX API). The BEAM VM code is compiled to machine code and runs directly on the CPU. As peerst explained, if you write your own C code in an Erlang port driver for example, you don't have to use RTEMS at all.

Is there the ability to run multiple OS processes or is the BEAM VM the only thing running after boot?

You can only run one process in RTEMS (hence the name The Real-Time Executive for Multiprocessor Systems), however you can simulate other processes via threads. This is how we run the network stack and Wi-Fi configuration tools among other things.

I've always thought that erlang has a much more natural mapping onto hardware (especially multicore hardware) than lisp.

Yes we boot the BEAM on the hardware.

The distinction between an OS and a language VM is blurry. When the language VM has such robust support for concurrency and IPC, the distinction is, in terms of functionality if not name, pretty much obliterated.

It makes me wonder if anyone has made VMs using the virtualization hardware in modern computers. Nested page tables seem exceptionally useful just as a jumping off point. Maybe the fact that they would still have to use the native instruction set is the limiting factor.

Love the bookshelf in the background of Peer Stritzinger's video feed. FreeBSD, UNIX, and a huge row of O'Reilly books on the bottom shelf! I think O'Reilly are some of the best, most thoroughly reviewed technical books out there, I always choose O'Reilly if the topic exists as they seem to vet their authors quite well and make sure they have competent subject matter experts actually write and review the books!

#phsycialbooks #FTW

I wonder if this will support Joxa or Lisp-Flavored-Erlang. Those are pretty much all I use on the Erlang VM nowadays, and I would love to get more into embedded stuff.

Because it is the full Erlang BEAM VM it can run any byte code compiled for it, including Joxa or LFE. However, we only have extra helper tooling for Erlang and Elixir at the moment. You can create a release manually and include any dependencies you want though.

Oh!! That's super cool, I think I will contribute then.

Assuming that I'm not a completely incompetent at programming (which admittedly might be a stretch :) ), would you be open to someone making a PR and adding Joxa or LFE tooling?

This is really cool. You can find out more about the project at https://grisp.org

how does this compare to nerves?

Nerves is Linux with an Erlang init(1), built with buildroot, and using sysfs for peripheral I/O. This is BEAM on an RTOS, which makes it effectively bare-metal.

Well to be technical an RTOS is not effectively baremetal. But I agree that it is extremely 'close to the metal'.

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